This Electric Solenoid (air valve) is used with air horns that require an on-board air system for 12 volt vehicles . Made of chrome plated metal housing. When the vehicle's horn button is depressed, the Solenoid becomes electrically energized, opening its chamber and permitting air pressure to reach the horn. The solenoid remains engaged as long as the horn button is depressed. Valve is rated up to 185 PSI air pressure. Male thread air outlet screws in to any horn that has a 1/4" female thread air inlet. Includes a 1/8" male thread x 1/4" compression fitting, that can accommodate a 1/4" outer diameter hose connection. Valve Size: 3-1/4" x 2"